just finished doing up a 1993 nc31 project big 1 . filled carbs with fuel pressed the starter a couple of times and she fired up and sounded good although only firing on 3 pots. stopped engine checked coils, carb etc, all ok. tried to start her up but the starter would not spin. turned engine back using a spanner on crankshaft but sill no spin. removed starter clutch but it was fine. moved crank back and forth to pin point clunk in engine. removed clutch cover and spotted conrod hanging down at pot 4. and expecting the worst took the head off. pulled out the piston to find it in perfect condition as was the cylinder bore, rings etc. took out conrod to find crank and shells undamaged. my problem now is finding a rod to replace the snapped one as information on this bike is scarce. the engine is a nc23e,have noticed this engine code is on several bike models but are the rods interchangeable? a bit of a mystery as to what caused this problem as did not hear any odd noises when bike was running. done all the checks before hand except a compression test as plug hole is too deep for my tester. any input welcome, in fact any info on setting up cams, torques etc very welcome.

would this be the same bud ??

http://www.ebay.co.uk/itm/HONDA-CB400-S ... 4ad5ab6814

thanks for reply, will make enquiries on this item, the problem now is the numbers on mine have not matched any for sale so sellers won't guarantee a fit. the number on their rod shaft matches mine but the number on the base clamp is different and we don't know what it means. have got a few sellers keeping an eye out for me. cheers.

quick update if anyone is interested, stripped engine down to find a hairline crack at the base of number 4 barrel = replacement barrels now needed. also the conrod has hit the bottom crankcase causing a tiny dimple on the outside. have been offered an engine for £200 that looks like it's been buried for 200yrs and another for £400 tatty but not run for 5yrs.

http://www.bertiesbikebreakers.com/

mate try these guys in chorley they are very helpfull and have massive stocks of stuff. Worth a phone call .

thanks again for info. after all the time spent on this little beast, powder coating, taper bearings, chain, mirrors, painted calipers, wheels , forks, swingarm, shocks, seals, etc,etc. I am at this minute trying to decide whether to take a deep breath and carry on or have a cb400,kawasaki zr550 bonfire in the back garden. [ built the zr to similar spec about 2yrs ago, painted it Kawasaki green for the missus but it's a bit heavy for her so its been wrapped up since.] just looked at berties and it's only 45 mins away. would anyone be interested in seeing any pics behind this little problem I'm having?

we love pics

dont give up bud i was same with my fzr400 it took me 18months to set carbs up properly had head off and all sorts but it wasnt going to beat me ..

have now fitted replacement engine. stripped down damaged engine and found no evidence for a reason for the conrod failure. it was a very low mileage engine that had a full engine service with a small squirt of oil in each cylinder before running the unit. I believe hydrolock was to blame, this is when too much fuel enters the cylinder and when on the compression stroke tries to compress the fuel but cannot so bends and snaps the conrod. the engine was running very smooth on tickover for a few minutes until I heard a metallic ping. I was also using a temp fuel tank.

Could you possibly have had a water leak into that cylinder, that could definately have bent a con rod.

yes Superjack that is a good possibility, basing it on there was a strong smell of fuel and the plug on that cylinder was soaked in fuel. must admit when I dropped the oil it was full of petrol and there was signs of a little coolant also. cases I've read about were mainly caused by water and a few by fuel ( my xs1100 was a pain for flooding my cylinders with fuel). also the engine had never run for a good few years, maybe a little head gasket corrosion had set in. have checked everything on the replacement engine and stripped (again) the carbs, replaced various bits and bobs on all 4 carbs (very expensive) ready to run soon. cheers for your input.